beforeEach(() => { window['__zone_symbol__FakeAsyncTestMacroTask'] = [ { source: 'HTMLCanvasElement.toBlob', callbackArgs: [{ size: 200 }] } ]; }); it('toBlob should be able to run in fakeAsync', fakeAsync(() => { const canvas: HTMLCanvasElement = document.getElementById('canvas') as HTMLCanvasElement; let blob = null; canvas.toBlob(function(b) { blob = b; }); tick(); expect(blob.size).toBe(200); }) );